German Pat. No. 32 18 676 discloses deaerating agents for aqueous coating systems with polymeric organic film formers. The agents contain 5 to 60% by weight of a linear polymer dissolved in an organic solvent, the polymer having at least 5 laterally bonded groups, each of which contains a silicon atom which is linked over a bivalent hydrocarbon group to the polymer. At least one group of the formula O-[C.sub.n H.sub.2n O-].sub.x Q is attached to the silicon atom. In this group, n=2 to 8, x - 1 to 10, Q is an alkyl group with 1 to 18 carbon atoms, an aryl group, an alkaryl group or an aryl group with 2 to 18 carbon atoms and the sum of the carbon and oxygen atoms of the R.sup.1 group is .gtoreq.5.
An agent is preferred which contains a compound of formula ##STR3## as linear polymer, wherein R.sup.1 has the above meaning and R.sup.2 and R.sup.3 are the same or different and represent, for example, a methyl group, Z are terminal groups, R.sup.7 may be hydrogen or, for example, an alkyl group, u.gtoreq.5 and the ratio u/v.gtoreq.0.4.
These agents have proven their value for the elimination of so-called microfoam and thus as deaerating agents. They are, however, only moderately effective as defoamers for organic systems.
In German Offenlegungsschrift No. 23 21 557, a method is described for the synthesis of block copolymers with polyether and, optionally, partially hydrogenated polydiene blocks which are connected to one another over organosilicon bridging elements. These block copolymers are used as additives for the preparation of polyurethane foams, stabilizing the foam formed and counteracting the collapse of the foam. The block copolymers are also intended to be used as release agents, demulsifiers and textile preparation agents and in cosmetics. In cosmetic preparations, they are said to improve the sliding ability and affect the consistency of creams and ointments.
Surprisingly, it has now been discovered that such compounds are particularly effective as defoamers and/or deaerating agents in organic systems, such as crude oil, mineral oil, paints and lacquers. The structure of these compounds is so variable that it can be adapted to the system in which the compounds are to be used. For example, the solubility of the block copolymer in the organic system can be adjusted in the desired manner by means of the ratio of the polysiloxane blocks to the organic carbon portion, especially the polyether blocks.